With most of my work I have to spend a lot of time thinking about how to integrate complex design and a myriad of colors within a form. Iridescent Vases are great because I can play with pure form and color and not stress about the other stuff.
The iridescence is caused by exposing the molten interior of the vase to a weak acid. The acid evaporates and is gone in a moment. The result is a rich and permanently etched surface that refracts and reflects the light surrounding it.
These images are of Josh's glass currently in private collections... not available for purchase.